Best way to mirror duplicate a rigged object?
Few explanations about the method to do it, but I have found nothing conventional to apply here on this initial particular (but well working) way of rigging a wing.

This was mainly manual editing (so not sure to remember all the steps) :


define a center and set a center bone at this location
parent the first wing bone to this center bone
rename the bones with .LEFT as suffix, select them all and "symetrize" to obtain the .RIGHT bones
duplicate wing parts and feathers and scale X, -1, with the center previously defined as pivot
Edit each part of the right wing in order to arrange the normals
Parent (with automatic weights) the wings (not the feathers) with the armature
For the feathers (on the right), select them by group (object mode) in order to bone parent to the corresponding wing part


And the result as given in the comments above : 

Nothing "magical" !!